"dead rubber" meaning in English

{
  "forms": [
    {
      "form": "dead rubbers",
      "tags": [
        "plural"
      ]
    }
  ],
  "head_templates": [
    {
      "args": {},
      "expansion": "dead rubber (plural dead rubbers)",
      "name": "en-noun"
    }
  ],
  "lang": "English",
  "lang_code": "en",
  "pos": "noun",
  "senses": [
    {
      "categories": [
        {
          "kind": "other",
          "name": "English entries with incorrect language header",
          "parents": [
            "Entries with incorrect language header",
            "Entry maintenance"
          ],
          "source": "w"
        },
        {
          "kind": "topical",
          "langcode": "en",
          "name": "Sports",
          "orig": "en:Sports",
          "parents": [
            "Human activity",
            "Human behaviour",
            "Human",
            "All topics",
            "Fundamental"
          ],
          "source": "w"
        }
      ],
      "glosses": [
        "In a series of sporting fixtures, a match of which the result is irrelevant, the winner of the series having already been determined by earlier results."
      ],
      "id": "en-dead_rubber-en-noun-5r0j4Lqs",
      "links": [
        [
          "sports",
          "sports"
        ],
        [
          "series",
          "series"
        ],
        [
          "match",
          "match"
        ],
        [
          "result",
          "result"
        ],
        [
          "irrelevant",
          "irrelevant"
        ],
        [
          "winner",
          "winner"
        ],
        [
          "determined",
          "determined"
        ]
      ],
      "raw_glosses": [
        "(sports) In a series of sporting fixtures, a match of which the result is irrelevant, the winner of the series having already been determined by earlier results."
      ],
      "topics": [
        "hobbies",
        "lifestyle",
        "sports"
      ]
    }
  ],
  "word": "dead rubber"
}

{
  "forms": [
    {
      "form": "dead rubbers",
      "tags": [
        "plural"
      ]
    }
  ],
  "head_templates": [
    {
      "args": {},
      "expansion": "dead rubber (plural dead rubbers)",
      "name": "en-noun"
    }
  ],
  "lang": "English",
  "lang_code": "en",
  "pos": "noun",
  "senses": [
    {
      "categories": [
        "English countable nouns",
        "English entries with incorrect language header",
        "English lemmas",
        "English multiword terms",
        "English nouns",
        "en:Sports"
      ],
      "glosses": [
        "In a series of sporting fixtures, a match of which the result is irrelevant, the winner of the series having already been determined by earlier results."
      ],
      "links": [
        [
          "sports",
          "sports"
        ],
        [
          "series",
          "series"
        ],
        [
          "match",
          "match"
        ],
        [
          "result",
          "result"
        ],
        [
          "irrelevant",
          "irrelevant"
        ],
        [
          "winner",
          "winner"
        ],
        [
          "determined",
          "determined"
        ]
      ],
      "raw_glosses": [
        "(sports) In a series of sporting fixtures, a match of which the result is irrelevant, the winner of the series having already been determined by earlier results."
      ],
      "topics": [
        "hobbies",
        "lifestyle",
        "sports"
      ]
    }
  ],
  "word": "dead rubber"
}